length vs fundamental measure

length and fundamental measure both are nouns.

Word	Noun	Adjective	Verb	Adverb
length	Yes	No	No	No
fundamental measure	Yes	No	No	No

As nouns, fundamental measure is a hypernym of length; that is, fundamental measure is a word with a broader meaning than length:

length: the linear extent in space from one end to the other; the longest dimension of something that is fixed in place
fundamental measure: one of the four quantities that are the basis of systems of measurement

Other hypernyms of length include physical property, dimension, fundamental quantity.

length (noun)	fundamental measure (noun)
a section of something that is long and narrow	one of the four quantities that are the basis of systems of measurement
the linear extent in space from one end to the other; the longest dimension of something that is fixed in place
continuance in time
the property of being the extent of something from beginning to end
size of the gap between two places